Study: Shock waves can damage eyes

Aug. 1, 2014 - 04:51PM
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An Army medic checks the eyes of a Marine during a medevac mission in Afghanistan. New research shows the shock waves of IED blasts can damage the eyes of nearby troops even if they are not injured by shrapnel. (Army photo)

A decade ago, the Defense Department launched a combat eye protection program that contributed to a drop in war-related eye injuries.

But making troops wear protective glasses apparently goes only so far. A new study by the University of Texas San Antonio and U.S. Army Institute of Surgical Research has found that blast waves themselves — not just the dirt and debris propelled by the blast — can cause significant and permanent damage to the eyes.

In an experiment that had the scientists blasting away at pig eyes with a high-powered air cannon, researchers learned the shock wave alone can damage portions of the eye, including the sclera — the white part — the retina, the optic nerve and more.

Among the most commonly seen injuries in the blasted porcine eyeballs was retinal detachment.

“Detachment is more common to older adults. But two clinicians on our team, an Army optometrist and ophthalmologist, told us this was something they were seeing in troops and couldn’t explain. That gave us the idea to look for this sort of damage in this study,” said Mathew Reilly, assistant professor of biomedical engineering at UTSA.

DoD data shows that ocular injuries account for 13 percent of all battlefield injuries and roughly 80 percent of eye injuries in combat are associated with blasts.

Reilly said his team undertook the study because while medical evidence has shown that blast waves appear to cause eye damage, few studies have been done to actually document the injury.

The research, he said, could lead to improved diagnosis at the time of injury and, eventually, better eyewear.

“Primary blast can cause damage to the the eye. If we don’t look for it, we’re not going to try to prevent it or diagnose these injuries,” Reilly said.

To conduct the study, researchers, including Reilly, Army ocular trauma expert Col. Jeff Cleland and others, used a shock tube and pig eyes obtained from a slaughterhouse.

They exposed the porcine eyes to pressure waves of various levels, simulating different sizes of blasts and proximity, videotaping the process and measuring pressure with sensors.

The results showed that even eyeballs exposed to lower pressures had damage.

Pig eyes are similar in structure to human eyes but with one difference — they are firmer.

“This could mean that our results underestimate the level of damage caused by a shock wave to the human eye,” Reilly said.

Future research, he said, will look at computer models for protective eye wear and similar experiments to test materials developed by those models to protect service members’ vision from a shock wave.

“I wasn’t in the military, but I would like those who serve our country to be better protected in the field or give them better diagnostics when they are injured,” Reilly said. “I am just trying to give back.”